As is well known, Venetian blinds of the type indicated above consist of a plurality of slats that can be packed flat, placing them in contact with each other, or extended to cover the area of a window, for example.
It is also known that the slats can be adjusted by rotating them relative to a horizontal plane, to give a plurality of positions. These positions range between the position in which the slats are essentially horizontal, and therefore do not obscure the window area, and the position in which the slats completely obscure the window area.
To pack or extend the slats, a winding apparatus generally comprising two or more cords attached to the slats is provided. Winding or unwinding these cords causes the slats to pack or unwind in the plane of the window.
The angular orientation of the slats can also be adjusted using cords attached to two sides of the slats. By acting on either one end or the other of the cord the slats are made to rotate about a horizontal plane. It will be clear from the above that the angular adjustment is the same for all the slats, which are therefore made to rotate simultaneously as one.
The prior art includes apparatuses which by a single rotation of a motorized shaft actuate both the slat packing and extending means, and the means that adjust the slat angle.
During the phase of extension it is preferable that the slats be locked in a predetermined angular position, also known as the “third position”, corresponding to an angle of about 38° relative to the horizontal plane. It is preferable for the resetting of the said third position to occur during the phase of packing and only after a certain number of rotations of the shaft actuating the apparatus. For this purpose the prior art includes mechanisms which delay the locking of the adjustment means, consisting for example of an axial sequence of discs which in sequence lock onto each other until they lock the angular setting of the slats.
These mechanisms are not particularly effective because the interaction between the individual discs occurs only when one is locked onto the next. In addition, these mechanisms require a lot of axial space and increase the weight of the structure of the apparatus.
The problem solved by the present invention is that of providing a Venetian blind and an apparatus for adjusting the position of the slats of Venetian blinds, whose structural and functional characteristics shall be such as to fulfil the abovementioned requirements and at the same time to overcome the abovementioned drawbacks cited with reference to the prior art.